Protection of wire-splices



Jan. 10, 1961 E. w. BOLLMEIER ETAL 2,967,795

PROTECTION OF WIRE-SPLICES Filed Oct. 18, 1955 States Patent PROTECTIONOF WIRE-SPLICES Emil Wayne Bollmeier, Mendota Township, Dakota County,and Leo F. Vokaty, New Canada Township, Ramsey County, Minn., assignorsto Minnesota Mining & Manufacturing Company, St. Paul, Minn., acorporation of Delaware Filed Oct. 18, 1955, Ser. No. 541,146

8 Claims. (Cl. 154-222) This invention relates to the protection ofsplices in wires and cables, and provides for the encapsulation ofspliced areas with liquid resinous insulating and protecting materialswhich are then solidified in place. The encapsulated splice area iscompletely covered and protected with a solid, tough, waterproofinsulating covering. The method is applicable to the protection of awide variety of shapes and sizes of splices. The coverings are appliedquickly and easily regardless of the contour of the underlying article.The resinous material completely fills all voids within the splice areaand, when solidified, provides positive and complete protection.

Typical examples of the method employed, the apparatus and materialsused, and the completed article resulting, are illustrated in theappended drawing, in which:

Figure 1 represents one method of insulating and protecting awire-splice, employing a unitary package of resinous materials, andbeing shown partly in section;

Figure 2 represents the preliminary steps, Figure 3 being a section ofFigure 2 as indicated, and Figure 4 represents the final product, of analternative method;

Figure 5 is an illustration, partly in section, showing the insulatingand protecting of a T-splice, using an injection port as shown inperspective in Figure 6a, or an alternative port as shown in sideelevation and partly in section in Figure 6b; and

Figure 7 is an alternative apparatus, shown mainly in section, forinjecting liquid solidifiable insulating resin into the splice area.

Figure l illustrates'a line or running splice between twoinsulation-covered stranded conductors 10 and 11, which is protected andinsulated with resinous material introduced from a capsule 15, andmaintained in position during the solidification period by a preformed,somewhat rigid, and preferably transparent envelope 12 of any desiredspecific configuration but here illustrated as globular. The envelope isshown as held in place on the outer surface of the insulated conductor10 by means of a wrapping of adhesive tape 13, and on the insulatedconductor 11 by the close-fitting but elastic and slidable friction sealportion 14 of the envelope 12; but both ends may be sealed by eithermethod. The envelope is perforated so as to permit theentry of the openend tip 16 of the capsule 15, through which the solidifiable liquidresin provided in the capsule is introduced, under pressure, into theenvelope and around the spliced areas of the conductors.

Rather than employ a preformed fitted envelope 12, suitable strips ofplastic or elastic film or sheet material, such as stretchable elasticvinyl film coated with pressuresensitive tape adhesive, may be woundloosely around the splice area to form a non-rigid envelope ofapproximately the same configuration as envelope 12. The film or tape isfastened in place on each of the insulated conductors, and perforated topermit the entry of the resinous mixture. The liquid resin is forcedthrough the aperture into the envelope and around the splice by pressureapplied to the flexible capsule 15, thereby distending the non-rigidenvelope to substantially the shape of the preformed envelope 12 ofFigure 1.

A preferred procedure is indicated in Figures 2-4. The splice areaconnecting the conductors 20 and 21 is first wrapped with a strip orstrips of insulating screen 22 to a shape and thickness capable ofproviding adequate protection for the cable. The screen is furthercovered and held in place by an overlapping and closely conformingspiral wrapping of non-porous adhesive tape 23. The spliced conductors20a, 21a, and the wrapping of screen 22 are shown in cross-section inFigure 3, taken at section 33 of Figure 2. The tape Wrapping is sealedtightly to itself and to the insulated cable to form a smooth covering44 as illustrated in Figure 4, and the covering is perforated, as at 26,to provide for entry of the resin from the capsule 25. The liquidsolidifiable resin from the capsule is forced through the perforationinto the space within the tape wrapping, Where it penetrates the screen22 and fills all voids within the splice area. Air or gas retainedaround the splice is forced out either through openings unavoidablyremaining at the ends of the tape wrapping 44, or between the severalstrands of the conductors, or through suitable further perforationsprovided for the purpose. The capsule is removed, as indicated in Figure4 which shows a drop 27 of the resin protruding from the perforation inthe wrapping 44, and the resin is permitted to solidify. A furtherWrapping of adhesive tape may be placed around the filled envelope toseal the openings during the latter period if found desirable.

The porous screen filler provides support for the flexible covering 44.The combination of filler and cover thus provides an envelope which isanalogous to the somewhat rigid envelope 12 of Figure l in maintainingits original shape and position during introduction of the liquid resin.

The structure provided in Figure 5 is somewhat similar to that ofFigures 2-4 in employing a sealed wrapping 54 of overlapping non-porousadhesive tape and a builtup porous screen spacer portion 53. There is inaddition an outer pressure wrap 55 of overlapped flexible strip materialhaving high tensile strength and low-stretch. A material such as. astrip of glass cloth, or filament-reinforced pressure-sensitive adhesivetape, or transparent film pressure-sensitive adhesive tape havingadequate tensile strength and resistance to stretch, is useful for thispurpose. Paper tapes are not ordinarily as high in tensile strength butare useful for less critical applications. An injection port 56aprovides a port of entry for the liquid solidlfiable resinouscomposition which is to be forced into the interior of the covering froma capsule 57 having a tip 58. The port 56a is shown in Figure 6a in moredetail; it consists of a tube 61a having a terminal flange or collar 62awhich is taped to the screen-covered splice area as shown in Figure 5.This type of port must be manually plugged as soon as the envelope isfilled and the nozzle 58 is withdrawn; or the nozzle 58 may itself serveto plug the port if held in place during solidification of the resin. Amodified self-sealing port 561; illustrated in Figure 6b includes aone-way valve member d3 consisting of a cross-slit hemisphericalflexible cup afiixecl within the tube 61b near the flange 62b.

The stranded conductors 51, 52 and 59 of Figure 5 are connected in aT-splice by means of a conventional connector member C, which may be,for example, a screw-threaded brass fitting or a lead or solder casting.The resulting splice is quite complicated in contour as compared withthat of Figure 2, yet the protective covering is applied with facilityand the protectedsplice is equally symmetrical and attractive inappearance. The resin completely fills all initial voids in the coveredarea,

3 the air being displaced as described in connection with Figures 2-4;The tip 58 may be held in place over the port to prevent loss of resinwhile the resin solidifies; or other means of sealing the tip during thesolidification cycle, such as the self-closing port of Figure 6b, may beemployed. The port 56a may be placed at any convenient location on thesplice covering, since the resin as it is forced around the splice willcompletely fill all voids and remove all enclosed air. To assist inremoval of air, a single strand of plastic filament, e.g., from thescreen 53, may be placed along the cable beneath the end of the outerwrapping of tapes 54 and 55. Such a device also provides indicator meansfor determining when the envelope is completely filled with resin, sinceat that point a small bead of resin will be seen slowly emerging fromthe tape covering along the filament.

Another means of forcing liquid solidifiable resin into thesplice-covering is illustrated in Figure 7, which shows a refillable gunmember 70 consisting of a cylinder 71, a removable forward end member 72having a tip 73, a rearward end member 74, and a plunger member 75operated by a handle member 76. Mechanical advantage may be provided atthe handle member by screw thread, lever systems, or the like, notshown. A flexible bag 77 fitting within the cylinder 71 contains theresin mixture. A corner 78 of the bag serves as a tip or snout portion,which is pulled through the tip 73 and cut to fit into the tube 61a ofthe port member 56:: of Figures 5 and 6a. Pressure applied to the handle76 then expels the resin from the bag 77 and forces it through theopening at the corner 78 into the interior of the covered splice area.The depleted bag is removed and discarded. leaving the gun 70 clean andin readiness for another cycle.

Solidifiable liquid resinous insulating material such as molten asphalt,Waxes. thermoplastic resins, etc. have long been used as pottingcompounds for protecting electrical components and such materials may beused here. However the use of self-curing liquid resinous mixturesprovides a number of additional advantages and is pre ferred. Forexample, the cured solidified resin is no longer thermoplastic.

The preferred resinous material is initially in the form of two or moreseparate components. When uniformly mixed together, this material is atfirst a thin liquid; but on standing for a short time, a reaction occursand the mixture is converted to a solid, tough, cured form. Manyresinous compositions are known which provide the desired result, butcertain epoxy resin compositions are outstanding for a number of reasonsand are preferred. With these mixtures the reaction is extremely rapid,the resin cures without evolution of volatile byproducts, the curedresin is highly resistant to moisture and is found to be firmly adheredto all components of the splice area. One such mixture is produced byseparately combining 46 parts by weight of Thiokol LP-Z liquid organicpolysulfide polymer with 8 parts of 2,4,6-tri(dimethylaminomethyl)phenol, and then intimately blending this mixture, just before use, with46 parts of Epon resin No. 562, a liquid epoxy resin containing freeepoxy radicals and produced from bisphenol and epichlorohydrin. Otherepoxy resins and other curing or hardening agents are also useful. Acoloring agent is frequently included in one of the two component partsof the final blend, in order visually to determine the effectiveness ofthe blending operation.

For use with two-part resinous compositions as just described, both thecapsule 15 of Figure 1 and the plastic envelope 77 of Figure 7 areinitially formed in two separate compartments, the two components of thereactive blend being separately contained therein. The structure isindicated in Figure l by the vestigial ring 17 on the innercircumference of the capsule 15, the ring being the remainder of a thinimpervious rupturable separator membrane initially separating the tworesin-forming materials. Just prior to application, the membrane isruptured by squeezing an end of the capsule, and the two materials arethen well blended by shaking and squeezing. The closed end of the tip 16is then cut off and the reacting mixture forced into the splice area.

The envelope 77 of Figure 7 is somewhat similarly constructed exceptthat the envelope walls are completely flexible. The walls arereleasably held together along a central line of the envelope and thetwo reactive components are separately contained in the two compartmentsthus provided. When desired for application, the contacting areas areseparated to permit the resin-forming components to be mixed together.The corner 78 is passed through the tip 73 and the end 72 assembled onthe cylinder 71 With the bag 77 inside. The handle and plunger assemblyis added, and the whole is then ready for use in forcing the reactingresin-forming mixture into the covered splice area.

Passage of air along the voids within the cable between the severalwires of the stranded conductor has been mentioned. The air is forcedfrom the splice area by the fluid resin, which then fills and seals theinterstices between the conductor strands, thus completely isolating thesplice area. In some instances it may be desirable to permit thecontinuous passage of an insulating fluid along the conductor, in whichcase it is only necessary to prewrap the stranded conductor with aprotective web such as an impervious adhesive tape or film, thus toprevent access of the liquid resin to the spaces between the strands.

Shielded cables require connections between the shielding as well asbetween the conductors. This may effectively be accomplished by placinga section of foil, wire, or wire gauze over the preliminary covering ofinsulating screen and in contact with the metal shield of the cable atthe extremities of the splice area. The whole is then covered withliquid-retaining and pressureresistant wrappings, precautions beingtaken to provide a port of entry for the subsequently applied resinousmixture to the splice area.

The insulating screen employed in the splice coverings of Figures 2 and5 provides a simple, effective means for spacing the outerliquid-retaining covering from the spliced conductor. A suflicientlythick and uniform layer of cured resin is thus assured around the splicearea so that any desired degree of electrical and mechanical protectionis provided. Coarse woven screen of plastic insulating material such asnylon, polyvinylidene chloride, or polyester polymers is particularlyeffective as the porous flexible insulating sheet material. The epoxyresin wets the surfaces of such polymers and bonds to such surfaces whencured in contact therewith, so that the final product is substantiallyhomogeneous and highly insulative as well as resistant to moisture andoil. Other fabricor screen-type webs or fibrous matts which provideadequate free space for penetration of the resinous liquid and which arenon-conductive and otherwise satisfactory are also useful.

The use of a built-up screen spacer thus makes possible the protectivecovering of splices of the widest variations in contour with a singlekit of materials including insulative screen strip, liquid-impervioussealing tape, selfhardening insulating resin composition, and pressureap plying means for applying the latter. In some instances, particularlyon larger installations, an additional element in the form of a hightensile strength tape or other means of providing a pressure-resistantcovering may be added. However, for smaller units and for operationsinvolving large numbers of splices of identical contour and dimension,equally effective and eflficient protective coverings are provided withkits in which a relatively rigid, closefitting casing, such as theenvelope 12 of Figure 1, replaces both the screen and the outerwrapping.

This application is a continuation-in-part of the cop'ending applicationSerial No. 386,992 of Emil Wayne Bollmeier and Leo F. Vokaty, filedOctober 19, 1953.

What is claimed is as follows:

1. A method of protecting wire and cable splices comprising: surroundingthe entire splice area with wrappings of open porous flexible andconformable insulating screen material to produce a compact, smoothlycontoured support structure full of interconnected open voids; applyingover and in contact with said support structure and adjacent cable areaa close-fitting flexibly conformable liquid-tight pressure-resistantcovering having a resin entry port; forcing a liquid self-curinginsulating resinous composition under pressure through said port to fillall voids within said covering; and permitting the resinous compositionto cure and solidify.

2. A method of protecting Wire and cable splices comprising: smoothlywrapping the entire splice area with open porous flexible andconformable insulating screen material in strip form to produce acompact, smoothly contoured support structure full of interconnectedopen voids; applying over and in contact with the support structure andadjacent cable area a close-fitting flexibly conformable liquid-tightpressure-resistant covering of overlapped courses of non-porous adhesivetape, said covering having a resin entry port; forcing a liquidselfcuring insulating resinous composition under pressure through saidport to fill all voids within said covering; and permitting the resinouscomposition to cure and solidify.

3. A method of protecting wire and cable splices comprising: smoothlywrapping the entire splice area with open flexibly screen-likeinsulating sheet material in strip form to produce a compact, smoothlycontoured support structure full of interconnected open voids; applyingover and in contact with the support structure and adjacent cable area aclose-fitting conformable liquid-tight pressure-resistant covering,including a first wrapping of flexible stretchable non-porous adhesivetape and a second wrapping of flexible stretch-resistant fibrousadhesive tape, and having a resin entry port; forcing a liquidself-curing insulating resinous composition under pressure through saidport to fill all voids within said covering; and permitting the resinouscomposition to cure and solidify.

4. A method of protecting wire and cable splices comprising: smoothlywrapping the entire splice area with open flexible screen-likeinsulating sheet material in strip form to produce a compact, smoothlycontoured support structure full of interconnected open voids; applyingover an area of said support structure an injection port member havingan extended conformable flat base and a centrally projecting tubularmember interiorly integrally provided with a one-Way valve member;applying over and in contact with said base and the remaining supportstructure and adjacent cable area a close-fitting conformableliquid-tight pressure-resistant covering, including a first wrapping offlexible stretchable non-porous adhesivev tape and a second wrapping offlexible stretch-resistant fibrous adhesive tape, while providing ventopenings for release of air from within said covering; forcing a liquidself-curing insulating resinous composition under pressure through saidtubular valve member to fill all voids within said covering; andpermitting the resinous composition to cure and solidify.

5. A cable splice structure in an insulated cable system, comprising: asplice area including interconnected bare conductor ends and adjacentinsulated cable; a compact, smoothly contoured insulating supportstructure, full of interconnected open voids, surrounding the entiresplice area; and a conformed close-fitting liquid-tightpressure-resistant flexible covering over and in contact with saidsupport structure and the adjacent cable area, said covering beingprovided with a resin entry port.

6. The structure of claim 5 in which the resin entry port comprises aprojecting tubular member having an extended flange-like baseconformably pressed against the outer surface of said support structureby said closefitting covering, said tubular member including an interiorintegral one-Way entry valve.

7. In the protection of splice areas in insulated cable systems, thesteps comprising: smoothly wrapping the splice with open-mesh flexiblescreen-like insulating sheet material in strip form to surround theentire splice area with a compact, smoothly contoured support structurefull of interconnected open voids; and app-lying over said supportstructure and adjacent cable area a tightly-fitting, fully conformable,liquid-tight, pressure-resistant covering including a wrapping offlexible stretchable nonporous adhesive tape and a wrapping of flexiblestretch resistant fibrous adhesive tape, said covering having a resinentry port.

8. An insulated electrical conductor component including a splice orconnection insulatively and protectively encapsulated within a smoothlycontoured support structure of insulating open-mesh screen materialcontained within an outer insulating envelope of overlapped flexiblestrip material in closely conformed contact therewith and completelyimpregnated and filled with a cured solid resinous insulatingcomposition.

References Cited in the file of this patent UNITED STATES PATENTS608,412 Patten et al. Aug. 2, 1898 2,099,370 Monnier Nov. 16, 19372,105,567 Webb Jan. 18, 1938 2,168,757 Baillard Aug. 8, 1939 2,190,054Cutter Feb. 13, 1940 2,312,652 Kornives et al. Mar. 2, 1943 2,536,173Hamilton Ian. 2, 1951 2,590,160 Dixon Mar. 25, 1952 2,632,211 Trigg Mar.24, 1953 2,730,473 Batezell Jan. 10, 1956 2,873,482 Bridge et a1. Feb.17, 1959 FOREIGN PATENTS 721,665 Great Britain Jan. 12, 1955

1. A METHOD OF PROTECTING WIRE AND CABLE SPLICES COMPRISING: SURROUNDINGTHE ENTIRE SPLICE AREA WITH WRAPPINGS OF OPEN POROUS FLEXIBLE ANDCONFORMABLE INSULATING SCREEN MATERIAL TO PRODUCE A COMPACT, SMOOTHLYCONTOURED SUPPORT STRUCTURE FULL OF INTERCONNECTED OPEN VOIDS, APPLYINGOVER AND IN CONTACT WITH SAID SUPPORT STRUCTURE AND ADJACENT CABLE AREAA CLOSE-FITTING FLEXIBLY CONFORMABLE LIQUID-TIGHT PRESSURE-RESISTANTCOVERING HAVING A RESIN ENTRY PORT, FORCING A LIQUID SELF-CURINGINSULATING RESINOUS COMPOSITION UNDER PRESSURE THROUGH SAID PART TO FILLALL VOIDS WITHIN SAID COVERING, AND PERMITING THE RESINOUS COMPOSITIONTO CURE AND SOLIDIFY.